He said: "It would be devastating to get to mile 24 and not complete the race. I couldn't see that happen. Everyone who runs has a good reason, I was running for my dad who died of cancer.

"I didn't want him to regret not finishing for the rest of his life."

Runners make their way over the start line during the 2016 Virgin Money London Marathon (Image: PA)

Will also took to Facebook to say that although he and Alex could have got faster times, the most important thing was helping someone else achieve their dream.

He said: "That lad wanted to get across that line. We were there to achieve our own goals, what ever they may have been. And helping that lad achieve his goal will stay with me forever."

The young man first collapsed around mile 24

Gregory, 28, from Isleworth added: "I was in a huge amount of pain myself as I was carrying a football injury and had several blisters on the feet but even with the pain of the run it would be so unfair for someone to miss out on a medal so close to the finish line, at least now for the rest of his life he can say he finished and he has a run time.

"I ran the marathon 2 years ago and although I was aiming to beat my previous time it was far more important to get this guy over the line and I'm really glad we did."